What is the volume of 50.0g of air?

Answer 1

The volume will vary depending on pressure and temperature.

The weighted average molecular mass of air is around 28.97 g/mole. This comes from percent calculation of the substances in air, like nitrogen and oxygen mostly. To know the volume of air, you must first ask at what pressure and temperature? I will assume standard P and T.

If you want to know the volume of a certain weigh of air, first find how many moles of air you have by dividing by the above amount

which equals

1.726 moles. Once you have the moles (n) of air, use the gas law PV=nRT

where R is 8.206 *10^-5 m^3*ATM/K*mol (be careful with units)

. Solving for V, you get V=nRT

/P. Using standard pressure of 1 ATM (pressure outside) and standard temperature (298K), 50g (1.726) of air would occupy .0422 m^3.

This can be reversed to find how many grams of air is in a given volume.
This gas law is not accurate with polar species because of strong intermolecular interactions, and only applies to "ideal gases". These theories get very deep and complex in thermodynamics, and are way beyond this discussion; but at low pressures and temperatures this law is pretty accurate.